Move lsp config to local file structure

.config/nvim/lsp/millet.lua

@@ -0,0 +1,19 @@
+---@brief
+---
+--- https://github.com/azdavis/millet
+---
+--- Millet, a language server for Standard ML
+---
+--- To use with nvim:
+---
+--- 1. Install a Rust toolchain: https://rustup.rs
+--- 2. Clone the repo
+--- 3. Run `cargo build --release --bin millet-ls`
+--- 4. Move `target/release/millet-ls` to somewhere on your $PATH as `millet`
+
+---@type vim.lsp.Config
+return {
+  cmd = { 'millet' },
+  filetypes = { 'sml' },
+  root_markers = { 'millet.toml' },
+}